Classical thermodynamic analyses of combustion processes consider only the combustion end states, due to an inability to analyze the high-speed, high-temperature chemical processes that occur before the end states are reached during the combustion event. As a result, accepted combustion analyses typically combine energy conservation laws with the requirement for end state equilibrium conditions to determine the range of energies expected to be available and accessible to the combustion products produced in an internal combustion engine.
Historically, it has been demonstrated that the efficiency of a combustion process increases slightly with increasing pressures. This increased efficiency has been attributed to the fact that most chemical reactions involved in combustion are known to proceed more completely when the pressure of the reaction is increased. It is also historically known that diesel combustion engines tend to produce more efficient combustion when the ratio of fuel with respect to air injected into the engine is decreased, in a fuel-air composition known as a lean-burn fuel mixture. It has additionally been demonstrated that the combustion event, being inherently an exothermic process, proceeds more completely at low temperatures relative to high temperatures. This has important consequences in that it is also well-known that production of unwanted combustion by-products, such as CO, H.sub.2, OH, H, O, and NO.sub.x, increases as the temperature of the combustion event increases.
These three well-known observations suggest that for optimization of combustion efficiency and simultaneous suppression of unwanted by-products like NO.sub.x, a combustion process should be controlled to proceed at a relatively high pressure and a relatively low temperature, and should employ a relatively lean fuel mixture. In practice, however, it has been demonstrated historically that lean fuel mixtures produce even higher NO.sub.x levels than conventional fuel-air ratios under normal combustion conditions; and further that high pressure combustion conditions cannot be maintained at low temperatures. This last result is, in fact, predicted by the thermodynamic equilibrium conditions and end-state analysis on which classical combustion theory is based, as mentioned above. Combustion technology and its classical theoretical underpinnings have thus heretofore produced only suboptimal fuel compositions and combustion processes.